Avalonia/samples/ControlCatalog.NetCore/NativeControls/Gtk/GtkHelper.cs

using System;
using System.Threading.Tasks;
using Avalonia.Controls.Platform;
using Avalonia.Platform.Interop;
using Avalonia.X11.Interop;
using Avalonia.X11.NativeDialogs;
using static Avalonia.X11.NativeDialogs.Gtk;
using static Avalonia.X11.NativeDialogs.Glib;

namespace ControlCatalog.NetCore;

internal class GtkHelper
{
    class FileChooser : INativeControlHostDestroyableControlHandle
    {
        private readonly IntPtr _widget;

        public FileChooser(IntPtr widget, IntPtr xid)
        {
            _widget = widget;
            Handle = xid;
        }

        public IntPtr Handle { get; }
        public string HandleDescriptor => "XID";

        public void Destroy()
        {
            RunOnGlibThread(() =>
            {
                gtk_widget_destroy(_widget);
                return 0;
            }).Wait();
        }
    }


    public static INativeControlHostDestroyableControlHandle CreateGtkFileChooser(IntPtr parentXid)
    {
        return GtkInteropHelper.RunOnGlibThread(() =>
        {
            using (var title = new Utf8Buffer("Embedded"))
            {
                var widget = gtk_file_chooser_dialog_new(title, IntPtr.Zero, GtkFileChooserAction.SelectFolder,
                    IntPtr.Zero);
                gtk_widget_realize(widget);
                var xid = gdk_x11_window_get_xid(gtk_widget_get_window(widget));
                gtk_window_present(widget);
                return new FileChooser(widget, xid);
            }
        }).Result;
    }
}